Current supply circuits having current regulating arrangements which provide a load current depending on a desired value signal are sufficiently known. DE 37 41 765 A1 and DE 38 13 066 A1 in each case describe such current regulating arrangements formed as switching regulators.
For current regulating purposes, current regulating arrangements of this type require a detection of the load current flowing through the load. Particularly in the case of current regulating arrangements provided with a large operating range, a high resolution and a high accuracy, the need arises to accurately detect the load current actually flowing. This problem emerges particularly for the “lower” operating range where small currents are made available whose values amount to only a fraction of the largest possible currents at the “upper” end of the operating range. In this case, for exact detection of the load current, it is necessary to work with external, high-precision components since circuit elements in integrated circuits achieve the desired accuracy and resolution only with a considerable trimming outlay. However, these external components contribute to increasing the production costs.
In the case of current regulators formed as switching regulators in which a semiconductor switch is opened and closed in a clocked manner for the purpose of supplying current to the load, the current measurement is additionally made more difficult since a high-frequency signal resulting from the clocked driving of the switch is in this case superposed on the load current. The influence of this high-frequency signal on the measurement signal rises as the load current decreases, that is to say the influence increases in the lower operating range.
In the case of current regulating arrangements known heretofore, regulation in the lowermost current range has therefore been dispensed with, or the corresponding resolution and accuracy have been adapted to the measurement accuracy technically possible.
It is an aim of the present invention to provide a current supply circuit for a load and a method for supplying current to a load in which a supply of current to the load is ensured over a wide operating range, in particular even with small currents, with a precisely adjustable load current.